This invention relates generally to grinding mills (ball and tube mills) used for grinding materials such as raw material for cement and more particularly to liners of the inner surfaces of the shells or drums of grinding mills.
More specifically, the invention relates to a drum lining in a grinding mill which lining has a working surface of a unique shape such that the grinding media such as steel balls placed in the drum are positively classified by size from large-diameter grinding media to small-diameter grinding media successively disposed from the drum feed inlet end to the discharge outlet end.
In general, the drum of a grinding mill contains therein a great variety of grinding media (e.g., steel balls) of different sizes. It is desirable, in order to attain a high grinding efficiency, that these grinding media be distributed according to the particle size thereof successively from large grinding media at the mill feed inlet to small grinding media near the discharge outlet. In actual practice, however, this distribution sequence tends to be reversed because of the flow of the material being ground within the drum.
For this reason, in order to obtain the desired distribution of the grinding media, it has heretofore been the practice in a mill of the instant type to line the inner wall surface of the drum with numerous lining units having inclined surfaces which become higher from the mill feed inlet toward the discharge outlet. However, since these lining units are aligned in rows in the circumferential direction of the mill drum, ring-shaped shoulders or ledges are formed in the circumferential direction on the inner surface of the drum by the upper ends of the inclinations of these lining units. These ring-shaped shoulders obstruct the migration of the grinding media, particularly grinding media of large diameter, toward the mill feed inlet. For this reason, in grinding mills of these class known heretofore, the classification or sorting of the grinding media has been inadequate, whereby desirable grinding efficiencies could not be attained.